Electronic components used in mobile communication equipment, such as portable phones are required to have a small size and a small weight without having their performance decline. A transmission circuit of the mobile communication equipment includes a low pass filter for preventing emission of unnecessary signals, such as higher harmonics. FIG. 12 shows a laminated low pass filter (LPF) as a conventional high frequency laminated device. The LPF includes sheets 101a to 101d, input/output terminal 102, ground (GND) terminal 103, inductors 104 and 105 printed as electrode patterns on the sheet 101b, capacitors 106, 107, and 108 printed as electrode patterns on the sheet 101c, and GND pattern 109 printed as an electrode pattern on the sheet 101d. FIG. 13 shows an equivalent circuit of the LPF.
In the LPF, the printed electrode patterns are located as close to each other as possible in order to allow the device to have a reduced size. The LPF, having an excessively reduced size, as shown by solid line F of FIG. 14, does not suppress high frequency bands sufficiently. This is caused due to mutual magnetic interference particularly between the inductors 104 and 105. Dotted line E shows an ideal characteristic of the LPF without the mutual magnetic interference.
In order to allow the LPF to have the small size, a space between the electrode patterns of inductors 104 and 105 adjacent to each other is narrow. But, the narrow space has the LPF have a declining performance as the characteristic shown in FIG. 14.
An inductance (L) at a frequency (ω) of an inductor formed of an electrode pattern having a characteristic impedance (Z) and an electrical length (θ) is expressed as the following equation:L=(Z·sinθ)/ω  (Equation 1)
In order to reduce an area occupied by the electrode pattern while the inductance (L) is maintained in constant, the characteristic impedance (Z) is increased, and the electrical length (θ) is accordingly reduced. That is, the area occupied by the electrode pattern is reduced by making the electrical length (θ) smaller to make the electrode pattern shorter.
However, since the sheet 101a to 101d have certain dielectric constants, the sheets 101a to 101d need to be thick, or the electrode pattern need to be thin in order to increase the characteristic impedance (Z). The thick sheets 101a to 101d would be contrary to the small size of the LPF. Moreover, thinning of electrode patterns available at present, which have widths of 100 μm, decreases an electrical conductivity of electrode patterns and increases an insertion loss of the LPF. Further, it is difficult to mass-produce the thin electrode patterns because of problems, such as scratch in printing. Accordingly, it is difficult to reduce the size of the conventional LPF, a high frequency device having the laminate structure.